DLR's Airborne F-SAR System

Andreas ReigberMicrowaves and Radar Institute

Slide 2

Why Airborne SAR?

Advantages of airborne SAR:• Higher SNR & resolution than spaceborne sensors

• Flexible operation of the sensor• Experimental platform for new technology

For the Institute:• Defining the „state‐of‐the‐art“ in SAR sensor technology

• Prepare future satellite missions• Test and develop new signal processing algorithms

• Development and demonstration of new products and imaging techniques

• Execution of scientific flight campaigns

development & demonstration of new technology

demonstration of new techniques with existing spaceborne systems

concepts for future spaceborne systems

Airborne‐SAR

Slide 3

P-ban

d

C-b

and

X-b

and

L-ban

d

The Advanced Airborne Sensor F‐SAR

F-SAR technical characteristics

X C S L P

RF [GHz] 9.6 5.3 3.2 1.3 0.35BW [MHz] 800 400 300 150 100PRF [kHz] up to 12Rg res. [m] 0.2 0.4 0.5 1.0 1.5Az res. [m] 0.2 0.3 0.35 0.4 1.5PolSAR ✓ ✓ ✓ ✓ ✓Rg cov [km] 12.5 (at max.bandwith) Sampling 8 Bit real; 1000MHz; 4 channels.

Remarkable features:‐ Very high resolution and SNR‐Multispectral operation (up to 4 bands)‐ Polarimetry in all bands‐ Single‐pass interferometry at X and S‐band‐Modular sensor design

Main Goals:• Defining the „state‐of‐the‐art“ in SAR sensor technology

• Scientific flight campaigns, preparation of new satellite missions

• New approaches by multispectral & high resolution PolSAR imaging

Slide 4

DLR’s New F‐SAR Sensor

F‐SAR core modules X‐bandrack

C/S‐bandrack

L‐bandrack

P‐bandrack

R1 R21 2

XCS-BandUPCE4

XCSChirp

E4

X-BandAntenna Switch

E2a

1H 1V 2H 2V 3H 3V 1H 1V 2H 2V

S-BandAntenna Switch

D3u, D3o

C-BandAntenna Sw.

D4

1H 1V

ADCADC1

C5

ADCADC2

C5

L-BandAntenna Sw.

F3

1H 1V

P-BandAntenna Sw.

A3

1H 1V

ADCADC5

C5

ADCADC6

C5

Disk Array 1B2

Disk Array 2B2

System Control

B4

OnboardProcessor

C7

STC/AGCProcessor

C5

Timing UnitC6

DC/AC Power Supply

C1

Navigation & Flight Guidance

System C2

S1,2

S1 S2

X1H X1V X2H X2V X3H X3V S1H S1V S2H S2V C1H C1V L1H L1V P1H P1V

R1X R2X R1S R2S R1C R2C

R5 R6

R1L R2L R1P R2P

L-Band UPCF5

LChirp

F5

S1

S2

S1

PChirp

A5

X-BandTWTA

E1

SCTWTA

D1

XCSDown Converter

E3

L-BandHPAF1

P-BandHPA A1

F5 L-Band Down Conv.

A5 P-Band Down Conv.

2 of 4 Switch C6

MDRMDR1

C3

MDRMDR2

C3

MDRMDR5

C3

MDRMDR6

C3

3 4 5 6

7

8

SC Ant. Sw.

D2

Mon

itor B

us

F-SAR Basic Configuration (Rack B and Rack C)

X-Band Rack E

SC-BandRack D

P-Band UPCA5

P-BandRack A

L-BandRack F

modularcabin layout

F‐SARsystem layout

The Advanced Airborne Sensor F‐SAR

F‐SAR „in action“ (mounted on research plane Do228)

Slide 6

Kaufbeuren (Germany)TerraSAR‐X, X‐band VV, HRS mode1.0m x 2.0m resolution

Kaufbeuren (Germany)F‐SAR, X‐band, VV polarisation0.25m x 0.25m resolution

Kaufbeuren (Germany)F‐SAR, X‐band quadpol (HH, VV, HV)0.25m x 0.25m resolution

Simulation of Future Spaceborne Products

Slide 7

Oensingen (Switzerland)F‐SAR, S‐Band quadpol (HH, HV, VV)0.5m x 0.65m resolution, 5 looks

Simulation of Future Spaceborne Products

Slide 8

Real‐time Situation Monitoring

F‐SAR (DLR‐HR)

data downlink: 1.25 GBit/sec (DLR‐KN) laser / microwave

Data distribution toend‐users (BOS, THW,red cross) throughcentral platform

real‐time onboard processingweather independentday & night capability

Slide 9

Real-time Situation MonitoringReal‐time Situation Monitoring

Slide 10

InSAR: Generation of digital elevation models

Kaufbeuren (Germany)Tandem‐X Digital Surface ModelKaufbeuren (Germany)F‐SAR Digital Surface Model

Muriel

InSAR: Generation of digital elevation models

INSARDEM XS (Scale around: 41m)

ALS 26032013 (Scale around: 41m)

Difference [-1m,1m]

InSAR DEM

Laser DEM

Difference

Easting

Northing

4

‐4

4

Laser DEM

InSARDEM (Scale around: 41m)

-2

0

2Laser (Scale around: 41m)

-2

0

2InSAR DEM Laser DEM 2

‐2

2

‐2

µ = ‐0.15m  σ =  0.11mDifference

Easting

Northing

INSARDEM XS (Scale around: 41m)

-4

0

4ALS 26032013 (Scale around: 41m)

-4

0

4InSAR DEM Laser DEM4

‐4

4

‐4µ = 0.21m  σ =  0.22m

Testsite: Jade BightF‐SAR Digital Surface Modelvs. ALS Reference Heights

Slide 12

DInSAR: Measurement of Ground Deformation / Motion

SWISAR campaign (2006 & 2007)

Hamm (Germany)deformation within 6 months

DINSAR campaign (2009)

Aletsch glacier (Switzerland)1‐day ice motion

85 cm / day

20-40 cm / year

RGB = L/X/P-Band

Estimated Forest Height

Polarimetric Interferometry: Estimation of Forest Height and Biomass

Azim

ut

L-band HH

Courtesy of K. Papathanssiou

y

z

x

n

r

bl

h

VVVH

HVHH

SSSS

S ][ 1

VVVH

HVHH

SSSS

S ][ 2

12

PolInSAR

Fichtelgebirge / GermanyCorridor / SpainBayrischer Wald / GermanyTraunstein / GermanyOberpfaffenhofen / Germany

Courtesy of

Polarimetric Interferometry: Estimation of Forest Height and Biomass

Slide 15

3D SAR Tomography• Innovative method for3D‐imaging• Possible applications: 

• Vegetation structure, biomass• 3D City models• Archeology

y

z

x

N parallel tracks(ca. 5‐20)

n

r

L

Hn

Slide 16

Circular SAR Imaging

360°illumination

r ≈ 6km

antenna illumination

xy

z

• Possibility of extremly high resolution (up to λ/4,   i.e. about 6cm at L‐band)

• Possibility of “holographic” 3D imaging

• Possibility of continous imaging (“video SAR”)

Circular SAR

Stripmap SAR

C‐Band X‐Band

Circular SAR Imaging: Continuous Monitoring

Polarimetric P-band Sounding

• Dedicated imaging mode for deep sounding of ice / bedrock structure • Long wavelength can penetrate very deep in dry (i.e. cold) ice.• Identical antennas as in SAR mode, but nadir‐looking by modified feed network.

clutterclutter?

bedrock

HV polarisation (single acquisition, low altitude)

32 km

~ 570m

Spitzbergen (Nordaustlandet)Sounder Image, P‐Band 350MHz

Holographic Ice Sounding / Multi-circular SAR

L‐Band P‐Band

Kangerlussuaq / K‐TransectFully polarimetric HoloSAR images. Pauli decomposition R,G,B = HH‐VV, HV, HH+VV.

ARCTIC15F‐SAR CAMPAIGN April ‐May 2015

Slide 20

space-/airborne bistatic geometry

v=7km/s

v=85m/s

Bistatic SAR Imaging & Processing

TerraSAR-X (Tx) F-SAR (Rx)

bistatic image azimuth resolution 0.5m

• Development of synchronisation techniquesin preparation of TanDEM‐X

• Development of new processing concepts(BFFB ‐ bistatic fast factorised back‐projection)

v=7000m/s

v=85m/s

monostatic bistatic

monostatic bistatic

Slide 21

Agriculture (crop parameters, soil moisture) 

Airborne‐SAR Campaigns (since 2001)

Forestry (forest heights and biomass)Surveys over sea and land iceSea topography and oceanography

?

Mission Proposal for Environment and Climate:

Advanced high‐performance SAR‐Technology:• Formation flight with two SAR‐satellites • Polarimetric interferometry and tomography• Digital Beamforming with large reflector antenna

• 11 test‐sites in Greenland• Analysis of several novel methods

for the estimation of snow and iceparameters

• Evaluation of high‐resolution SAR forsecurity applications in Arctic environments

• Study of the stongly varying penetrationcapabilities of the different bands intosnow and ice

• Demonstration of multi‐spectral SARdata recording in 4 frequency bands

• Acquisition of unique data setsfor further research 

F‐SAR Campaign ARCTIC/DALOX (May 2015)

Campaign test sites

ARCTIC15 Helheim Glacier, differences in L‐, S‐ and X‐ band.Fully polarimetric images. Pauli decomposition R,G,B = HH‐VV, HV, HH+VV.

F‐SAR CAMPAIGN April ‐May 2015

X‐Band

L‐Band

S‐Band

ARCTIC15 Helheim Glacier, differences in L‐, S‐ and X‐ band.Fully polarimetric images. Pauli decomposition R,G,B = HH‐VV, HV, HH+VV.

F‐SAR CAMPAIGN April ‐May 2015

X‐Band

L‐Band

S‐Band

Increasin

g  pen

etratio

n de

pth

X‐Band

C‐Band

L‐Band

P‐Band (non‐simultaneous)

ARCTIC15 K‐Transect ‐ Percolation zoneFully polarimetric images. Pauli decomposition R,G,B = HH‐VV, HV, HH+VV.

F‐SAR CAMPAIGN April ‐May 2015

ARCTIC15 Sea Ice between Greenland and North AmericaFully polarimetric images. Pauli decomposition R,G,B = HH‐VV, HV, HH+VV.

F‐SAR CAMPAIGN April ‐May 2015

L‐Band

S‐Band

X‐Band

ARCTIC15 Godhavn, X‐band detail image, 25cm resolutionFully polarimetric images. Pauli decomposition R,G,B = HH‐VV, HV, HH+VV.

F‐SAR CAMPAIGN April ‐May 2015

BIOMASS: ESA Earth Explorer Mission

System: Fully-polarimetric P-band SAR 12 m reflector antenna Strip-map acquisition mode with 6 MHz

bandwidth Spatial resolution: 60 x 50 m with 6 ENL Launch planned for 2021

ESA EE-7 to map forest above-ground biomass and its changes

PolSAR Pol-InSAR Combined TomoSAR

AfriSAR Campaign 2016

Goals:• Preparation of ESA‘s BIOMASS mission • Algorithm development for Tandem‐L• Various test‐sites in Gabun (tropical rain forest)• Cooperation with ESA, NASA/JPL, NASA/Goddard, Onera• Extensive ground‐truthing

Execution:• Flight campaign by Onera in July 2015• F‐SAR campaign in February / March 2016• Parallele flights by UAVSAR and LVIS in March 2016

Results:• SAR acquisitions in L‐ and P‐band quadpol• Reflectivity, PolInSAR, Tomography• Simulation of BIOMASS products• Estimation of forest heights and biomass• Evalutation and development of BIOMASS and Tandem‐L algorithms

AfriSAR Kampagne: Kalibrierung

L-Band P-BandNkok calibration test site

(0°22'43.34"N, 9°36'30.80"E)

surface

double

volume

AfriSAR Campaign: Results

Pongara test site: mangroves(0° 9'15.29"N, 9°28'46.56"E)

L‐Band

P‐Bandsurface

double

volume

AfriSAR Campaign: P-Band Mosaic (7 tracks)

P-Bandsurface

double

volume Lopé test site: rain forest / savannah(0°12'41.06"S, 11°33'11.58"E)

Current Developments: Digital Beamforming (DBF) Extension

FutureRequirements

imaging mode (quad pol)Mode X Mode Y Mode Z

Resolution 5 m 1 m << 1 mSwath 400 km 100 km 30 kmOrbit Duty Cycle 30 Minutes per Orbit

Modus Y

Modus Z

ModusX

AD

Digital Beam Forming

AD

AD

AD

AD

SAR Processing

x x x x x

AD

1 2

a1

3 4 5

a2 a3 a4 a5

SAR Processing

x Mixing

radar withphased array

radar with DBF

Possibilities:• Better radiometric accuracy• Moving target detection• Ambiguity suppression• RFI suppression• Adaptive & hybrid SAR imaging modes

• …

F‐SAR: Next Steps…

F-SAR digital system X-band rack

C/S L PF‐SA

RDBFSA

R

DBF digital systemDBF X-band

rack

F‐SAR: 2+2 Kanäle à 500MHz

DBFSAR:12 Kanäle à 2 GHz

Maximum data rate DBFSAR:8.5 GByte /sec

(Factor 12 to F‐SAR)

Ka-band rack

DBF‐SAR: First X‐band in‐flight results (April 2017)